US soldier Bradley Manning has been jailed for 35 years for giving WikiLeaks more than 700,000 US military and diplomatic documents.
The 25-year-old was convicted last month of espionage, theft and other charges in the biggest leak of classified information in American history.
He was acquitted of aiding the enemy, the most serious of the charges against him.
Sitting before a military judge at Fort Meade in the US state of Maryland, Manning was also told he would be dishonourably discharged from the US army and will forfeit some pay.
Manning's lawyer announced he is to formally request that US President Barack Obama pardons his client.
Speaking at a news conference after following the sentencing, David Coombs said: "The time to end Bradley Manning's suffering is now.
"The time for our president to focus on protecting whistle-blowers instead of punishing them, is now. The time for our president to pardon Bradley Manning is now."
WikiLeaks founder Julian Assange hailed the sentencing a "significant tactical victory" but said the former US soldier's trial and conviction was an "affront to western justice".
In a statement, he said: "While the defence should be proud of their tactical victory, it should be remembered that Mr Manning’s trial and conviction is an affront to basic concepts of Western justice...
"Mr Manning’s treatment has been intended to send a signal to people of conscience in the US government who might seek to bring wrongdoing to light. This strategy has spectacularly backfired, as recent months have proven.
"Instead, the Obama administration is demonstrating that there is no place in its system for people of conscience and principle. As a result, there will be a thousand more Bradley Mannings."